1. Field of the Invention
At least an embodiment of the present invention relates to a solenoid valve device used in, for example, an automatic transmission of a vehicle, and a method for manufacturing the same.
2. Description of the Related Art
A control valve is typically provided in an automatic transmission of a vehicle to control a transmission system. The control valve controls the transmission system by supplying a hydraulic pressure of a predetermined magnitude to the transmission system or stopping the supply using a solenoid valve device.
Such solenoid valve devices are described in, for example, JP-A 2003-207069 and JP-A 1999-173449. The solenoid valve device described in JP-A 2003-207069 is an on-off solenoid valve, and this solenoid valve device includes a nozzle in which a valve body is accommodated, and a solenoid to drive the valve body. The solenoid includes a cylindrical case, and a bobbin around which a coil is wound, a fixed core, and a rod pin arranged to reciprocate in a center of the coil are accommodated in the cylindrical case. In the solenoid valve device, the coil of the solenoid is energized to cause the rod pin to reciprocate, and a tip of the rod pin causes opening and closing of the valve body.
When a solenoid valve device is attached to a control valve, a nozzle with an O-ring fitted to an outer circumference thereof is typically fitted into an attachment hole, with the result that a gap between the nozzle and a wall surface of the attachment hole is sealed with the O-ring, as is the case with each of the solenoid valve devices described in JP-A 2003-207069 and JP-A 1999-173449. However, this related-art technique involves use of a sealing member made of a resin, such as the O-ring, and as the resin inevitably degrades due to aging, the sealing member needs to be periodically replaced in the case where the solenoid valve device is used for a long term, as when the solenoid valve device is used in a vehicle. For example, a sealing member made of a nylon resin, which is widely used, or the like may degrade as a result of the resin hydrolyzing by absorbing surrounding water.
Moreover, the sealing member is made of a resin softer than the materials of the solenoid valve device and the control valve, and it is therefore required to take great care, when fitting the nozzle of the solenoid valve device into the attachment hole of the control valve, to prevent the sealing member from making contact with an edge of the attachment hole and being damaged, which would result in a reduction in sealing performance. As a result, the operation of fitting the solenoid valve device may take much time.
Accordingly, a solenoid valve device as described below has been proposed. In this solenoid valve device, a nozzle is made of a metal, and accuracy with which a circumference of the nozzle is worked is accordingly improved to minimize a gap between the nozzle and the wall surface of the attachment hole, and thus, sufficient sealing performance is secured without use of a sealing member.
The solenoid valve device of this type has the advantage of freedom from a degradation of a sealing member due to aging, damage to a sealing member during fitting of the nozzle, and the like, but it is difficult to manufacture such a related-art solenoid valve device because the nozzle thereof is entirely made of a metal. In particular, in the solenoid valve device, it is necessary to arrange a movable valve body in the nozzle, and define hollow portions, such as an in-port, an out-port, and a valve chest, in the nozzle, and therefore, it is much more difficult to manufacture the nozzle entirely made of a metal than a nozzle made of a resin and involving use of a sealing member.
At least an embodiment of the present invention, for example, enables a solenoid valve device to be fixed to a control valve with excellent sealing performance with use of a nozzle made of a resin and without use of a sealing member such as an O-ring.